Shunting of Guns or Parts


The phenomenon of the secondary current bypasses the nugget being formed is called shunting.


Since shunting always reduces the actual welding current, it should be avoided whenever possible. There are two primary sources of shunting. (1) Shunting due to existing spot welds, as shown in Fig. 1.

Shunting of Guns or Parts - Production Engineering

Fig. 1. Shunting due to existing spot weld

(2) Shunting due to design, as shown in Fig. 2, where shunting inevitably occurs in series welding process.

Shunting of Guns or Parts and Poor Weld Accessibility - Production Engineering

Fig. 2. Shunting in series welding process
(Source: GM Automotive Welding Handbook)


If the following weld issues occur, it may very well suggest the incorrect electrode dressing:


Quality, Workplace Issues, Cost, Downtime, Maintenance, Throughput (cycle time; PPH), are all potentially affected by this condition. Special considerations are noted below:

Quality: a lot of weld quality issues will occur due to shunting: Undersized weld, Stuck weld, Inconsistent weld quality, Brittle weld, Nonround weld, and Poor Class A appearance.

Workplace Issues: shunting of gun or work sheet in certain extreme cases may be hazardous if not being properly prevented.

Subordinate Causes

  • The weld position is too close to an existing weld.
  • Inappropriate series welding design.